Compositions comprising a cyclohexanedione herbicide and an adjuvant

ABSTRACT

A novel herbicidal composition comprising a 2-(substituted benzoyl)-1,3-cyclohexanedione and an organic phosphate, phosphonate or phosphinate adjuvant at a concentration of less than 0.5% v/v when added to a spray tank as a tank mix additive or when co-formulated with a herbicide to produce a spray tank concentration of less than 0.5% v/v is disclosed.

The present invention relates to a herbicidal composition, to its preparation and use. In particular is relates to a herbicidal composition which demonstrate improved activity over the prior art compositions.

The protection of crops from weeds and other vegetation that inhibits crop growth is a constantly recurring problem in agriculture. To help combat this problem, researchers in the field of synthetic chemistry have produced an extensive variety of chemicals and chemical formulations effective in the control of such unwanted growth. Chemical herbicides of many types have been disclosed in the literature and a large number are in commercial use. Commercial herbicides and some that are still in development are described in The Pesticide Manual, 12th edition, published in 2000 by the British Crop Protection Council.

Many herbicides also damage crop plants. The control of weeds in a growing crop therefore requires the use of so-called ‘selective’ herbicides which are chosen to kill the weeds while leaving the crop undamaged. Few selective herbicides are selective enough to kill all the weeds and leave the crop completely untouched. In practice, the use of most selective herbicides is actually a balance between applying enough herbicide to acceptably control most of the weeds whilst causing only minimal crop damage.

One important class of selective herbicides are 2-(substituted benzoyl)-1,3-cyclohexanedione compounds disclosed, inter alia, in U.S. Pat. Nos. 4,780,127, 4,938,796, 5,006,158 and 5,089,046 the disclosures of which are incorporated herein by reference. A particularly preferred 2-(substituted benzoyl)-1,3-cyclohexanedione is mesotrione, chemical name 2-(2-nitro-4-methylsulfonylbenzoyl)-cyclohexanedione. This is known largely for use to selectively control weeds in a corn (maize) crop, both before the crop emerges from the ground (pre-emergent) and after (post-emergent).

EP0579052 discloses a plant treatment agent comprising at least one biocide and an accelerator which may be inter alia a phosphate. U.S. Pat. No. 2,927,014 discloses the use of a range of organic phosphonate and phosphinate compounds as herbicides. WO93/04585 discloses a herbicidal composition comprising at least one phosphonate or phosphinate and at least one compound selected from phenmedipham, desmedipham, metamitron, lenacil, ethofumesate and chloridazon. WO94/18837 teaches the use of a specific phosphonate, bis(2-ethylhexyl) 2-ethylhexyl phosphonate, as adjuvant to improve the bioperformance of specified of herbicides. However, the particular use of phosphonate and phosphinate in improving the efficacy of 2-(substituted benzoyl)-1,3-cyclohexanedione compounds is wholly unexpected.

Accordingly, the present invention provides a herbicidal composition comprising:

i) a 2-(substituted benzoyl)-1,3-cyclohexanedione of formula (I)

-   -   wherein X represents a halogen atom; a straight- or         branched-chain alkyl or alkoxy group containing up to six carbon         atoms which is optionally substituted by one or more groups —OR¹         or one or more halogen atoms; or a group selected from nitro,         cyano, —CO₂R², —S(O)_(m)R¹, —O(CH₂)_(r)OR¹, —COR², —NR²R³,         —SO₂NR₂R³, —CONR²R³, —CSNR²R³ and —SO₂R₄;     -   R¹ represents a straight- or branched-chain alkyl group         containing up to six carbon atoms which is optionally         substituted by one or more halogen atoms;     -   R² and R³ each independently represents a hydrogen atom; or a         straight- or branched-chain alkyl group containing up to six         carbon atoms which is optionally substituted by one or more         halogen atoms;     -   R⁴ represents a straight-or branched-chain alkyl, alkenyl or         alkynyl group containing up to six carbon atoms optionally         substituted by one or more halogen atoms; or a cycloalkyl group         containing from three to six carbon atoms;     -   each Z independently represents halo, nitro, cyano, S(O)_(m)R⁵,         OS(O)_(m)R⁵, (C₁-C₆)-alkyl, (C₁-C₆)alkoxy, (C₁-C₆)haloalkyl,         (C₁-C₆)haloalkoxy, carboxy, (C₁-C₆)-alkylcarbonyloxy,         (C₁-C₆)alkoxycarbonyl, (C₁-C₆)alkylcarbonyl, amino,         (C₁-C₆)-alkylamino, (C₁-C₆)dialkylamino having independently the         stated number of carbon atoms in each alkyl group,         (C₁-C₆)alkylcarbonylamino, (C₁-C₆)alkoxycarbonylamino,         (C₁-C₆)alkylaminocarbonylamino, (C₁-C₆)dialkylaminocarbonylamino         having independently the stated number of carbon atoms in each         alkyl group, (C₁-C₆)alkoxycarbonyloxy,         (C₁-C₆)alkylaminocarbonyloxy, (C₁-C₆)dialkylcarbonyloxy,         phenylcarbonyl, substituted phenylcarbonyl, phenylcarbonyloxy,         substituted phenylcarbonyloxy, phenylcarbonylamino, substituted         phenylcarbonylamino, phenoxy or substituted phenoxy;     -   R⁵ represents cyano, —COR⁶, —CO₂R⁶ or (O)X;     -   R⁶ represents hydrogen or straight- or branched-chain alkyl         group containing up to six carbon atoms;     -   R⁷ represents (C₁-C₆)alkyl, (C₁-C₆)haloalkyl, (C₁-C₆)cyanoalkyl,         (C₃-C₈)cycloalkyl optionally substituted with halogen, cyano or         (C₁-C₄)alkyl; or phenyl optionally substituted with one to three         of the same or different halogen, nitro, cyano,         (C₁-C₄)haloalkyl, (C₁-C₄)alkyl, (C₁-C₄)alkoxy or —S(O)_(m)R⁸;     -   R⁸ represents (C₁-C₄)alkyl;     -   each Q independently represents (C₁-C₄)alkyl or —CO₂R⁹ wherein         R⁹ is (C₁-C₄)alkyl;     -   m is zero, one or two;     -   n is zero or an integer from one to four,     -   r is one, two or three; and     -   p is zero or an integer from one to six; and     -   ii) an organic phosphate, phosphonate or phosphinate adjuvant at         a concentration of less than 0.5% v/v when added to a spray tank         as a tank mix additive or when co-formulated with a herbicide to         produce a spray tank concentration of less than 0.5% v/v.

Suitably, X is chloro, bromo, nitro, cyano, C₁-C₄ alkyl, —CF₃, —S(O)_(m)R¹, or —OR¹; each Z is independently chloro, bromo, nitro, cyano, C₁-C₄ alkyl, —CF₃, —OR¹, —OS(O)_(m)R⁵ or —S(O)_(m)R⁵; n is one or two; and p is zero.

Preferably, the 2-(substituted benzoyl)-1,3-cyclohexanedione of formula (1) is selected from the group consisting of 2-(2′nitro-4′methylsulphonylbenzoyl)-1,3-cyclohexanedione, 2-(2′-nitro-4′-methylsulphonyloxybenzoyl)-1,3-cyclohexanedione, 2-(2′-chloro-4′-methylsulphonylbenzoyl)-1,3-cyclohexanedione, 4,4-dimethyl-2-(4-methanesulphonyl-2-nitrobenzoyl)-1,3-cyclohexanedione, 2-(2-chloro-3-ethoxy-4-methanesulphonylbenzoyl)-5-methyl-1,3-cyclohexanedione and 2-(2-chloro-3-ethoxy-4-ethanesulphonylbenzoyl)-5-methyl-1,3-cyclohexanedione.

Suitably, the phosphate, phosphonate or phosphinate adjuvant is a compound of formula II

wherein R¹¹ is an alkoxy group containing from 4 to 20 carbon atoms or a group —[OCH₂CHR¹⁴]_(t)—OR¹⁵ wherein R¹⁴ is hydrogen, methyl or ethyl, t is from 0 to 50 and R¹⁵ is hydrogen or an alkyl group containing from 1 to 20 carbon atoms; and R¹² and R¹³ are independently (i) an alkyl or alkenyl group containing from 4 to 20 carbon atoms; (ii) optionally substituted phenyl; (iii) an alkoxy group containing from 4 to 20 carbon atoms or (iv) a group —[OCH₂CHR¹⁴]_(t)—OR¹⁵ as herein defined; or (v) a group of formula (III)

wherein R¹⁶ is an alkoxy group containing from 4 to 20 carbon atoms or a group —[OCH₂CHR¹⁴]_(t)—OR¹⁵ as herein defined and R¹⁷ is an alkyl group containing from 4 to 20 carbon atoms, optionally substituted phenyl, an alkoxy group containing from 4 to 20 carbon atoms or a group —[OCH₂CHR¹⁴]_(t)—OR¹⁵ as herein defined; and wherein t is from 0 to ten.

The term “alkyl” as used herein, including when used in expressions such as “alkoxy”, includes linear or branched chain alkyl groups. Optional substituents which may be present in optionally substituted phenyl include C₁₋₄ alkyl and halogen.

In a first embodiment of the invention, there is provided a herbicidal composition comprising a 2-(substituted benzoyl)-1,3-cyclohexanedione of formula (1) as hereinbefore defined, and a phosphate of formula (II), wherein R¹¹, R¹² and R¹³ are all independently alkoxy groups.

In a second embodiment of the invention, there is provided a herbicidal composition comprising a 2-(substituted benzoyl)-1,3-cyclohexanedione of formula (1) as hereinbefore defined, and a phosphonate of formula (II), wherein R¹¹ and R¹² are both independently alkoxy groups and R¹³ is an alkyl, alkenyl or optionally substituted phenyl group.

In a third embodiment of the invention, there is provided a herbicidal composition comprising a 2-(substituted benzoyl)-1,3-cyclohexanedione of formula (I) as hereinbefore defined, and a phosphinate of formula (II), wherein R¹¹ is an alkoxy group and R¹² and R¹³ are both independently an alkyl, alkenyl or optionally substituted phenyl group.

Optional alkoxylation of an ester group is represented by the group —[OCH₂CHR¹⁴]_(t)—OR¹⁵ as herein defined. It is preferred that the value of t is from 0 to 10 and more preferably from 0 to 5. If a range of degrees of alkoxylation is present, t may represent an average value and is not necessarily an integer. Similarly, mixed alkoxylation may take place such that different values of R¹⁴ are present in the group —[OCH₂CHR¹⁴]_(t). It is preferred that R¹⁵ is an alkyl group containing from 1 to 8 carbon atoms. If t is 0, the group —[OCH₂CHR¹⁴]_(t)—OR¹⁵ becomes alkoxy and when t is 0 therefore the group —OR¹⁵ is suitably alkoxy containing from 4 to 20 carbon atoms.

When the compound of formula (II) is a phosphate it is preferred that each of the groups R¹¹, R¹² and R¹³ are alkoxy groups containing from 4 to 10 carbon atoms. It is especially preferred that each of R¹¹, R¹² and R¹³ contain from 4 to 8 carbon atoms. Preferred phosphates are tri(2-ethylhexyl)phosphate and tributyl phosphate.

When the compound of formula (II) is a phosphonate, it is preferred that each of the groups R¹¹ and R¹² are alkoxy groups containing from 4 to 10 carbon atoms and R¹³ is an alkyl group containing from 4 to 10 carbon atoms. Suitable phosphonates are disclosed in WO 98/00021 and the present invention also includes equivalents wherein the relevant alkyl chain length is lower than that disclosed in WO 98/00021. It is especially preferred that each of R¹¹, R¹² and R¹³ contain from 4 to 8 carbon atoms. Preferred phosphonates are bis-(2-ethylhexyl)-2-ethylhexylphosphonate, bis-(2-ethylhexyl-octylphosphonate and bis-butyl-butylphosphonate, particularly bis-(2-ethylhexyl)-2-ethylhexylphosphonate.

When the compound of formula (II) is a phosphinate, it is preferred that R¹¹ is an alkoxy group containing from 4 to 10 carbon atoms and R¹² and R¹³ are both alkyl groups containing from 4 to 10 carbon atoms. It is especially preferred that each of R¹¹, R¹² and R¹³ contain from 4 to 8 carbon atoms. Suitable phosphinates are disclosed in WO 98/00021 and the present invention also includes equivalents wherein the relevant alkyl chain length is lower than that disclosed in WO 98/00021.

Suitably, the concentration of phosphate, phosphonate or phosphinate in the spray tank composition is in the range 0.01% to 0.49%, suitably in the range 0.025% to 0.49%, more suitably in the range 0.05% to 0.48%, and most preferably in the range 0.05% to 0.2%.

In the context of the present invention, the term “herbicidal composition” is intended to refer to pre-mix concentrate compositions and to the diluted tank-mix compositions.

Herbicidal compositions of the present invention may be formulated as a pre-mix concentrate which is diluted with, dissolved in or dispersed in water shortly before use. In the present invention, the concentrate generally comprises between 30 and 950 g/litre of the 2-(substituted benzoyl)-1,3-cyclohexanedione of formula (I), preferably 100 to 800 g/l, most preferably 150 to 500 g/l. The phosphate, phosphonate or phosphinate adjuvant added to the concentrate composition at a weight ratio of the herbicide to the phosphate, phosphonate or phosphinate of from 25:1 and 1:25 and especially 10:1 and 1:10 more especially 1:5 and 5:1. In addition, one or more further active ingredients, for example a second herbicide, may be added to the concentrate composition.

Alternatively, the herbicidal compositions of the present invention are the diluted spray tank composition. The spray tank composition may be obtained by diluting a pre-mix concentrate as described above to the required concentration and adding any other required adjuvants. Alternatively, the spray tank composition may be obtained by diluting a concentrate composition comprising only the 2-(substituted benzoyl)-1,3-cyclohexanedione of formula (I) to the required concentrate, and subsequently adding the required amount of phosphate, phosphonate or phosphinate along with any other required adjuvants. Adjuvants are normally applied as a percentage of the spray volume applied per hectare. Water volume per hectare is normally about 200 litres/ha but can vary from 50 to greater than 3000 for special applications. Adjuvants are nominally applied at volumes of from 0.05% to 1.0% of the spray volume per hectare. Taking 200 l/ha as an average, typical volume rates of adjuvant will therefore be in the region of 100 g (0.05%) to 2000 g (1.0%). Typical herbicide rates range from 10 g/ha to 1 kg. Therefore one skilled in the art will expect ratios which cover these typical use rates for both active and adjuvant. These relate directly to ratio (by weight) of compound of formula (I) to the compound of formula (II) from 50:1 to 1:400. It is preferred that the ratio by weight of the compound of formula (1) to the compound of formula (II) is from 25:1 and 1:25 and especially 10:1 and 1:10 more especially 1:5 and 5:1.

When the herbicidal composition of the invention is a pre-mix concentrate, it may thus be formulated as granules, as wettable powders, as suspension concentrates, as emulsifiable concentrates, as granular formulations, powders or dusts, as flowables, as solutions, as suspensions or emulsions. These formulations may contain as little as about 0.5% to as much as about 95% or more by weight of active ingredient. The optimum amount for any given compound will depend upon formulation, application equipment, and nature of the plants to be controlled.

Wettable powders are in the form of finely divided particles that disperse readily in water or other liquid carriers. The particles contain the active ingredient retained in a solid matrix. Typical solid matrices include fuller's earth, kaolin clays, silicas and other readily wet organic or inorganic solids. Wettable powders normally contain about 5% to about 95% of the active ingredient plus a small amount of wetting, dispersing, or emulsifying agent. If liquid compounds of Formula II are formulated as dry products such as WP (or WG), there will be a requirement to absorb/adsorb these into/onto suitable carriers for this formulation type.

Suspension concentrates are high concentration suspensions of solid herbicide in a liquid carrier such as water or an oil.

Emulsifiable concentrates are homogeneous liquid compositions dispersible in water or other liquid, and may consist entirely of the active compound with a liquid or solid emulsifying agent, or may also contain a liquid carrier, such as xylene, heavy aromatic naphthas, isophorone and other non-volatile organic solvents. In use, these concentrates are dispersed in water or other liquid and normally applied as a spray to the area to be treated. The amount of active ingredient may range from about 0.5% to about 95% of the concentrate.

Granular formulations include both extrudates and relatively coarse particles, and are usually applied without dilution to the area in which suppression of vegetation is desired. Typical carriers for granular formulations include sand, fuller's earth, attapulgite clay, bentonite clays, montmorillonite clay, vermiculite, perlite and other organic or inorganic materials which absorb or which can be coated with the active compound. Granular formulations normally contain about 5% to about 25% active ingredients which may include surface-active agents such as heavy aromatic naphthas, kerosene and other petroleum fractions, or vegetable oils; and/or stickers such as dextrins, glue or synthetic resins. Water emulsifiable granules can also be produced by appropriate means which are well know to those skilled in the art.

Dusts are free-flowing admixtures of the active ingredient with finely divided solids such as talc, clays, flours and other organic and inorganic solids that act as dispersants and carriers.

Formulations which are amenable to the production of mixed products are especially important since a compound of formula II will generally be an oil (or soluble in an organic solvent) and the 2-(substituted benzoyl)-1,3-cyclohexanedione derivatives of formula (I) will generally be highly insoluble in water and therefore most easily formulated as a dispersion in water (or an oil). Thus dispersions of multiple phases are the likely formulations of choice.

Other useful formulations for herbicidal applications include simple solutions of the active ingredient in a solvent in which it is completely soluble at the desired concentration, such as acetone, alkylated naphthalenes, xylene and other organic solvents. Pressurized sprayers, wherein the active ingredient is dispersed in finely divided form as a result of vaporization of a low boiling dispersant solvent carrier, may also be used.

Many of these formulations include wetting, dispersing or emulsifying agents. Examples are alkyl and alkylaryl sulphonates and sulphates and their salts; polyhydric alcohols; polyethoxylated alcohols; esters and fatty amines. These agents, when used, normally comprise from 0.1% to 15% by weight of the formulation.

Another suitable additive is crop oil concentrate (COC) which is well known for herbicides and is a mixtures of petroleum oils and non-ionic surfactants, available as, for example AGRI-DEX, PENETRATOR, and PENETRATOR PLUS and from Helena Chemical Company, HER-BIMAX from UAP, ES CROP OIL PLUS from Gromark, and CROP OIL PLUS, from Wilfarm, (83% paraffinic oil, 17% emulsifier surfactant). Other possible additives include urea ammonium nitrate, a fertiliser, methylated seed oil and ammonium sulphate.

Each of the above formulations can be prepared as a package containing the herbicide together with other ingredients of the formulation (other active ingredients, diluents, emulsifiers, surfactants, etc.). The formulations can also be prepared by a tank mix method, in which the ingredients are obtained separately and combined at the grower site.

The compositions of the present invention have been shown to be particularly effective in the control of weeds, particularly when compared to corresponding compound of formula (I) in the absence of phosphate, phosphonate or phosphinate. Accordingly, a further aspect of the invention provides a process for the control of weeds, said process comprising applying a herbicidally effective amount of a composition according to the invention to the locus of the weeds.

The composition of the invention may be used against a large number of agronomically important weeds, including Stellaria, Nasturtium, Agrostis, Digitaria, Avena, Setaria, Sinapis, Lolium, Solanum, Phaseolus, Echinochloa, Scirpus, Monochoria, Sagittaria, Bromus, Alopecurus, Sorghum halepense, Rottboellia, Cyperus, Abutilon, Sida, Xanthium, Amaranthus, Chenopodium, Ipomoea, Chrysanthemum, Galium, Viola, and Veronica. For purposes of the present invention, the term “weeds” includes undesirable crop species such as volunteer crops.

Controlling means killing, damaging, or inhibiting the growth of the weeds.

The “locus” is intended to include soil, seeds, and seedlings, as well as established vegetation.

The benefits of the present invention are seen most when the composition is applied to kill weeds in a growing crop, such as Maize (corn). The benefit of the invention is seen most with post-emergent application, but pre-emergent application is also possible.

The present invention is illustrated by the following Example in which all parts and percentages are by weight unless otherwise stated.

EXAMPLE 1

The activity of a number of compositions of the present invention was assessed. The weeds were Echinochloa crus-galli (ECHCG), Amaranthus tamariscinus (AMARE), Ipomoea hederacea (IPOHE), polygonum convolvulus (POLCO), Xanthium strumarium, (XANST), ?????? (DIGSA), ?????? (VIOAR) and ?????? (BRAPL). The results are given in Table 1. Products were sprayed at a range of g/ha (see table) in 2001/ha water volume and assessed after 21 days for bioefficacy. The activity is expressed as the percentage of weeds controlled. TABLE 1 Comparison of activity of mesotrione acid with standard adjuvants vs. activity of mesotrione acid with a compound of formula (II) Rate Mesotrione Treatment g/ha ECHCG XANST AMARE IPOHE POLCO VIOAR BRAPL DIGSA Mesotrione Acid + 10 84 53 58 55 0.5% MSO 20 13 92 58 78 67 40 70 92 88 83 84 80 75 96 90 77 95 160 97 98 89 80 96 320 99 Mesotrione Acid + 1% 10 73 63 20 53 COC 20 80 80 50 73 10 95 40 91 78 50 91 17.5 97 80 90 92 90 96 60 100 160 93.5 100 320 Mesotrione Acid + 1% 10 88 35 55 35 COC + 2.5% UAN 20 47 88 55 58 73 50 75 40 80 94 70 88 90 70 88 80 98 96 80 97 96 85.5 100 160 100 97 78 98 95 100 320 100 100 Mesotrione Acid + 0.5% 10 96 84 70 82 tributyl phosphate 20 45 96 88 84 70 40 55 96 90 80 88 80 88 99 97 78 99 160 95 98 95 87 99 320 99 Mesotrione acid + 0.5% 10 98 68 80 bis(2-ethylhexyl)-2- 20 93 96 75 97 100 ethylhexyl phosphonate 40 100 98 83 97 100 80 100 99 85 98 100 160 100 99 94 98 100 320 100 100 Mesotrione acid + 0.075% 10 88 63 65 33 bis(2- 20 79 75 73 73 28 98 ethylhexyl)2-ethylhexyl 40 93 89 78 85 40 100 phosphonate 60 94 93 77 97 78 100 80 88 100 160 320 Mesotrione Acid + 0.2% 10 83 80 63 53 bis(2- 20 96 78 90 99 57.5 100 ethylhexyl)2-ethylhexyl 40 95 90 88 95 75 100 phosphonate 80 95 90 89 95 98.5 100 160 94.5 100 320 Mesotrione Acid + 0.075% 10 80 55 33 50 tri(2- 20 95 83 75 87 48 96 ethylhexyl) phosphate 40 94 80 87 85 73 100 80 95 90 94 83 100 160 100 100 320 Mesotrione Acid + 0.2% 10 91 65 55 68 tri(2-ethylhexyl) 20 95 73 80 78 48 100 phosphate 40 96 90 97 93 73 100 80 97 92 94 95 83 100 160 100 100 320 

1. A herbicidal composition comprising: (i) a 2-(substituted benzoyl)-1,3-cyclohexanedione of formula (I)

wherein X represents a halogen atom; a straight- or branched-chain alkyl or alkoxy group containing up to six carbon atoms which is optionally substituted by one or more groups —OR¹ or one or more halogen atoms; or a group selected from nitro, cyano, —CO₂R², —S(O)_(m)R¹, —O(CH₂)_(r)OR¹, —COR², —NR²R³, —SO₂NR₂R³, —CONR²R³, —CSNR²R³ and —OSO₂R₄; R¹ represents a straight- or branched-chain alkyl group containing up to six carbon atoms which is optionally substituted by one or more halogen atoms; R² and R³ each independently represents a hydrogen atom; or a straight- or branched-chain alkyl group containing up to six carbon atoms which is optionally substituted by one or more halogen atoms; R⁴ represents a straight-or branched-chain alkyl, alkenyl or alkynyl group containing up to six carbon atoms optionally substituted by one or more halogen atoms; or a cycloalkyl group containing from three to six carbon atoms; each Z independently represents halo, nitro, cyano, S(O)_(m)R⁵, OS(O)_(m)R⁵, (C₁-C₆)-alkyl, (C₁-C₆)alkoxy, (C₁-C₆)haloalkyl, (C₁-C₆)haloalkoxy, carboxy, (C₁-C₆)-alkylcarbonyloxy, (C₁-C₆)alkoxycarbonyl, (C₁-C₆)alkylcarbonyl, amino, (C₁-C₆)-alkylamino, (C₁-C₆)dialkylamino having independently the stated number of carbon atoms in each alkyl group, (C₁-C₆)alkylcarbonylamino, (C₁-C₆)-alkoxycarbonylamino, (C₁-C₆)alkylaminocarbonylamino, (C₁-C₆)-dialkylaminocarbonylamino having independently the stated number of carbon atoms in each alkyl group, (C₁-C₆)alkoxycarbonyloxy, (C₁-C₆)-alkylaminocarbonyloxy, (C₁-C₆)dialkylcarbonyloxy, phenylcarbonyl, substituted phenylcarbonyl, phenylcarbonyloxy, substituted phenylcarbonyloxy, phenylcarbonylamino, substituted phenylcarbonylamino, phenoxy or substituted phenoxy; R⁵ represents cyano, —COR⁶, —CO₂R⁶ or —S(O)_(m)R⁷; R⁶ represents hydrogen or straight- or branched-chain alkyl group containing up to six carbon atoms; R⁷ represents (C₁-C₆)alkyl, (C₁-C₆)haloalkyl, (C₁-C₆)cyanoalkyl, (C₃-C₈)-cycloalkyl optionally substituted with halogen, cyano or (C₁-C₄)alkyl; or phenyl optionally substituted with one to three of the same or different halogen, nitro, cyano, (C₁-C₄)haloalkyl, (C₁-C₄)alkyl, (C₁-C₄)alkoxy or —S(O)_(m)R⁸; R⁸ represents (C₁-C₄)alkyl; each Q independently represents (C₁-C₄)alkyl or —CO₂R⁹ wherein R⁹ is (C₁-C₄)-alkyl; m is zero, one or two; n is zero or an integer from one to four; r is one, two or three; and p is zero or an integer from one to six; and (ii) an organic phosphate, phosphonate or phosphinate adjuvant at a concentration of less than 0.5% v/v when added to a spray tank as a tank mix additive or when co-formulated with a herbicide to produce a spray tank concentration of less than 0.5% v/v.
 2. A herbicidal composition according to claim 1, wherein X is chloro, bromo, nitro, cyano, C₁-C₄ alkyl, —CF₃, —S(O)_(m)R¹, or —OR¹.
 3. A herbicidal composition according to claim 1, wherein each Z is independently chloro, bromo, nitro, cyano, C₁-C₄ alkyl, —CF₃, —OR¹, —OS(O)_(m)R⁵ or —S(O)_(m)R⁵.
 4. A herbicidal composition according to claim 1, wherein n is one or two.
 5. A herbicidal composition according to claim 1, wherein p is zero.
 6. A herbicidal composition according to claim 1, wherein the compound of formula (I) is selected from the group consisting of 2-(2′nitro-4′methylsulphonylbenzoyl)-1,3-cyclohexanedione, 2-(2′-nitro-4′-methylsulphonyloxy benzoyl)-1,3-cyclohexanedione, 2-(2′-chloro-4′-methylsulphonylbenzoyl)-1,3-cyclohexanedione, 4,4-dimethyl-2-(4-methanesulphonyl-2-nitrobenzoyl)-1,3-cyclohexanedione, 2-(2-chloro-3-ethoxy-4-methanesulphonylbenzoyl)-5-methyl-1,3-cyclohexanedione and 2-(2-chloro-3-ethoxy-4-ethanesulphonylbenzoyl)-5-methyl-1,3-cyclohexanedione.
 7. A herbicidal composition according to claim 1, wherein the phosphate, phosphonate or phosphinate adjuvant is a compound of formula II

wherein R¹¹ is an alkoxy group containing from 4 to 20 carbon atoms or a group —[OCH₂CHR¹⁴]_(t)—OR¹⁵ wherein R¹⁴ is hydrogen, methyl or ethyl, t is from 0 to 50 and R¹⁵ is hydrogen or an alkyl group containing from 1 to 20 carbon atoms; and R¹² and R¹³ are independently (i) an alkyl or alkenyl group containing from 4 to 20 carbon atoms; (ii) optionally substituted phenyl; (iii) an alkoxy group containing from 4 to 20 carbon atoms or (iv) a group —[OCH₂CHR¹⁴]_(t)—OR¹⁵ as herein defined; or (v) a group of formula (III)

wherein R¹⁶ is an alkoxy group containing from 4 to 20 carbon atoms or a group —[OCH₂CHR¹⁴]_(t)—OR¹⁵ as herein defined and R¹⁷ is an alkyl group containing from 4 to 20 carbon atoms, optionally substituted phenyl, an alkoxy group containing from 4 to 20 carbon atoms or a group —[OCH₂CHR¹⁴]_(t)—OR¹⁵ as herein defined; and wherein t is from 0 to ten.
 8. A herbicidal composition according to claim 7, wherein the compound of formula (II) is a phosphate in which R¹¹, R¹² and R¹³ are all independently alkoxy groups.
 9. A herbicidal composition according to claim 7, wherein the compound of formula (II) is a phosphonate in which R¹¹ and R¹² are both independently alkoxy groups and R¹³ is an alkyl, alkenyl or optionally substituted phenyl group.
 10. A herbicidal composition according to claim 7, wherein the compound of formula (II) is a phosphinate in which R¹¹ is an alkoxy group and R¹² and R¹³ are both independently an alkyl, alkenyl or optionally substituted phenyl group.
 11. A process for the control of weeds, said process comprising applying to the locus of the weeds a herbicidally effective amount of a composition as claimed in claim
 1. 